A COMPARATIVE-STUDY OF OPTICAL TECHNIQUES APPLIED TO PARTICLE-ENHANCED ASSAYS OF C-REACTIVE PROTEIN

This work is based on the well-established immunoassay principle of ag glutination of latex particles covered by immunoproteins. In our exper iments, positively charged particles act as carriers for the F(ab')(2) fragment, obtained from rabbit polyclonal IgG, active against C-react ive protein (CRP). The presence of the antigen CRP in the immunolatex system causes agglutination and the aim of the present study was to co mpare different optical techniques (turbidimetry, nephelometry, angula r anisotropy and photon correlation spectroscopy) capable of detecting the agglutination. The sensitivity and detection limit largely depend on the optical method. We have analyzed for each optical technique th e following aspects: sensitivity, reproducibility, detection limit, re action time, amount of sample wasted and availability of the required detection device. The results presented in this paper show that both a ngular anisotropy and photon correlation spectroscopy offer lower dete ction limits, and use little reagent, but have longer assay times than the classical optical techniques of turbidimetry and nephelometry. (C ) 1997 Elsevier Science B.V.